He Xukun, Cheng Jiangtao, Patrick Collier C, Srijanto Bernadeta R, Briggs Dayrl P
Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
J Colloid Interface Sci. 2020 Sep 15;576:127-138. doi: 10.1016/j.jcis.2020.05.003. Epub 2020 May 4.
A liquid droplet is apt to be deformed within a compact space in various applications. The morphological change of a droplet and vapor accumulation in the confined space between two parallel surfaces with different gaps and surface wettability are expected to significantly affect the evaporation dynamics of the squeezed droplet therein.
Here the evaporation dynamics of a squeezed droplet between two parallel hydrophobic/superhydrophobic surfaces are experimentally explored. By reducing the surface gap from 1000 μm to 400 μm, the evolution of contact angle, contact radius and volume of the evaporating droplet are measured. A diffusion-driven model based on a two-parameter ellipsoidal segment geometry is developed to predict the morphology and volume evolution of a squeezed droplet during evaporation.
Evaporation dynamics of a squeezed water droplet via the constant contact radius (CCR) mode, the constant contact angle (CCA) mode, or the mixed mode are experimentally observed. Confirmed by our ellipsoidal segment model, the evaporation of the squeezed droplet is significantly depressed with the decreasing surface gap, which is primarily attributed to vapor enrichment in a more confined geometry. A linear scaling law between droplet volume and evaporation time is unveiled, which is verified by a simplified cylindrical model.
在各种应用中，液滴易于在紧凑空间内发生变形。预计在具有不同间隙和表面润湿性的两个平行表面之间的受限空间中，液滴的形态变化和蒸汽积聚将显著影响其中挤压液滴的蒸发动力学。
在此，通过实验探索了在两个平行的疏水/超疏水表面之间挤压液滴的蒸发动力学。通过将表面间隙从1000μm减小到400μm，测量了蒸发液滴的接触角、接触半径和体积的演变。建立了基于双参数椭球体段几何形状的扩散驱动模型，以预测挤压液滴在蒸发过程中的形态和体积演变。
实验观察到挤压水滴通过恒定接触半径（CCR）模式、恒定接触角（CCA）模式或混合模式的蒸发动力学。经我们的椭球体段模型证实，随着表面间隙减小，挤压液滴的蒸发显著受抑制，这主要归因于在更受限几何形状中的蒸汽富集。揭示了液滴体积与蒸发时间之间的线性比例定律，并通过简化的圆柱模型进行了验证。
